CVE-2026-44897 — MEDIUM (6.1)

Vulnerability Description

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, HTMLRenderer.heading() builds the opening <hN> tag by string-concatenating the id attribute value directly into the HTML — with no call to escape(), safe_entity(), or any other sanitisation function. A double-quote character " in the id value terminates the attribute, allowing an attacker to inject arbitrary additional attributes (event handlers, src=, href=, etc.) into the heading element. This vulnerability is fixed in 3.2.1.

CVSS Score

6.1

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Attack Vector

NETWORK

Attack Complexity

LOW

Privileges Required

NONE

User Interaction

REQUIRED

Scope

CHANGED

Confidentiality

LOW

Integrity

LOW

Availability

NONE

Affected Products

Vendor	Product	Versions
Mistune Project	Mistune	< 3.2.1

Related Weaknesses (CWE)

CWE-79

References

https://github.com/lepture/mistune/releases/tag/v3.2.1ProductRelease Notes
https://github.com/lepture/mistune/security/advisories/GHSA-v87v-83h2-53w7ExploitVendor Advisory

FAQ

What is CVE-2026-44897?

CVE-2026-44897 is a vulnerability with a CVSS score of 6.1 (MEDIUM). Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, HTMLRenderer.heading() builds the opening <hN> tag by string-concatenating the id attribute value directly into the HTML...

How severe is CVE-2026-44897?

CVE-2026-44897 has been rated MEDIUM with a CVSS base score of 6.1/10. Review the CVSS metrics above for detailed severity breakdown.

Is there a patch for CVE-2026-44897?

Check the references section above for vendor advisories and patch information. Affected products include: Mistune Project Mistune.